The present invention relates to fire doors and in particular to a fire door construction for use in elevators which is capable of withstanding ambient temperature extremes without destruction or undue warping of the door frame.
Heretofore, doors of this type have been constructed of front and back sheet paneling separated by metal frame spacers. The paneling is typically welded to each of the frame spacers.
Doors constructed in this fashion have heretofore been expensive since a considerable amount of labor time is required to fill and sand the welding blemishes on the door faces. In addition, such a rigid, essentially unitary, construction has been found to transmit an unacceptable level of background noise to the interior of the elevator.
Furthermore, under conditions of extreme ambient temperature changes, the unitary door structures, including the door frames, have been found to buckle severely thereby increasing the danger to elevator passengers. Such doors are frequently found to be commercially unacceptable during legally mandated testing procedures. The result is that the cost of doors which reach the market is higher than would otherwise be the case.